This invention relates in general to trocars for insertion into a body cavity for providing a conduit through the cavity wall to allow surgical procedures to be performed through the cannula without opening the cavity wall or to observe surgical procedures by means of a laparoscope inserted into the cannula of the trocar.
Such trocars typically consist of an outer cannula comprising a hollow tube through which an inner trocar is inserted. The inner trocar consists usually of a solid rod-like member having a sharp distal end for penetrating the wall of the body cavity. The trocar is inserted into a small incision in the body and the trocar is then placed in the incision and the inner trocar activated to penetrate the cavity wall. The inner cannula is then removed and the outer trocar is utilized to insert surgical instruments into the cavity or to insert a laparoscope into the cavity to enable the surgeon to observe the operation of other devices inserted into the body cavity through additional trocars in the body.
The laparoscope consists of an optical member which can conduct the image observed in the cavity to an external eyepiece or to an electronic display available to the surgeon. The laparoscope may also include a light source as well as other instruments required for the surgery to be performed.
One of the principal problems encountered in the use of such laparoscopes is that of clouding of the tip of the laparoscope from condensed moisture in the cavity or obscuring the end of the laparoscope by body fluids, blood or other organic material displaced by the surgical activity. The clouding may also be caused because of the temperature difference between the ambient air in the operating room and the temperature of the body. Typically, the temperature in the operating room is in the order of 20.degree. C. (68.degree. F.) while the temperature of the body cavity is in the order of 37.degree. C. (98.6.degree. F.). When the cooler instrument comes into contact with the warmer moist atmosphere of the body cavity, moisture from the atmosphere will condense on the end of the optical fiber fogging the view of the surgeon.
When the observing end of the optical fiber becomes obscured, either from bodily fluids or due to condensation, it is necessary to withdraw the laparoscope from the cannula and clean the end of the laparoscope. When the laparoscope is reinserted in the cannula it is often difficult to re-locate the exact field of the surgery thus extending the time for the procedure and frustrating the surgeon's efforts.
One solution to the condensation problem is to warm the laparoscope before inserting it in the cannula by immersing it in water at approximately body temperature or wrapping it in warm towels prior to use. While these actions may reduce or eliminate the condensation, they are not effective in preventing body fluids, blood and other organic matter within the body cavity from repeatedly obscuring the view of the surgeon.
In the prior art various devices have been described disclosing solutions to these problems. However, these solutions are generally complicated and expensive. For example, U.S. Pat. No. 5,225,001 discloses a device which incorporates as part of an endoscope an annular passage surrounding the optical fiber through which a cleansing fluid can be pumped using an electric actuator operating on a syringe located in the body of the device outside the body cavity. While this device is effective in cleaning the distal end of the optical fiber, it adds considerable additional complexity to the viewing instrument and no doubt increases its cost. Also, it does not efficiently clean the tip of the laparoscope as well as would be desired. Additionally, the inclusion of the annular channel within the viewing device requires a larger outside diameter for the instrument. In U.S. Pat. No. 5,167,220, a second tube is provided which is attached to the outer surface of the scope device for propelling a cleansing fluid across the viewing end of the fiber. This solution suffers from the same drawbacks as the previously described patent. In endoscopic instruments where substantial amounts of continuous irrigating fluid are required, there has been provided separate nozzles for directing some of the irrigating fluid across the viewing end of the optical fiber for clearing fluids and debris from the fiber. One such device is described in U.S. Pat. No. 3,835,842. However, again the cleansing function is incorporated as a part of the scope instrument with the above described disadvantages of complexity, lack of efficiency and additional cost.